US20120274416A1 - Ladder filter, duplexer and module - Google Patents
Ladder filter, duplexer and module Download PDFInfo
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- US20120274416A1 US20120274416A1 US13/454,940 US201213454940A US2012274416A1 US 20120274416 A1 US20120274416 A1 US 20120274416A1 US 201213454940 A US201213454940 A US 201213454940A US 2012274416 A1 US2012274416 A1 US 2012274416A1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
- H03H9/542—Filters comprising resonators of piezoelectric or electrostrictive material including passive elements
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
- H03H9/72—Networks using surface acoustic waves
- H03H9/725—Duplexers
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/0023—Balance-unbalance or balance-balance networks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/0538—Constructional combinations of supports or holders with electromechanical or other electronic elements
- H03H9/0566—Constructional combinations of supports or holders with electromechanical or other electronic elements for duplexers
Definitions
- a certain aspect of the present invention relates to ladder filters, duplexers and modules.
- RF filters particularly, those having a compact size and a sharp characteristic.
- the filters are required to generate an attenuation pole and have sufficient suppression over a broad band in order to handle a new communication system.
- Such filters may be a ladder filter in which multiple resonators are connected.
- a duplexer or module equipped with filters is required to have transmission and reception filters configured so that the transmission filter has high suppression in the pass band of the reception filter and the reception filter has high suppression in the pass band of the transmission filter.
- Japanese Patent Application Publication No. 6-350390 discloses a resonator with which an LC resonance circuit is connected in parallel.
- Japanese Patent Application Publication No. 11-55067 discloses a ladder filter to which an inductor is connected.
- the arts disclosed in Documents 1 and 2 are capable of generating an attenuation pole outside of the pass band.
- a ladder filter a duplexer and a module having high suppression over a broad band.
- a ladder filter including: at least one series resonator connected in series between an input terminal and an output terminal; at least one parallel resonator connected in parallel with the at least one series resonator; an additional resonator connected in series between the at least one series resonator and one of the input terminal and the output terminal; and an inductor connected to the additional resonator in series, the additional resonator having a resonance frequency higher than an anti-resonance frequency of the at least one series resonator.
- FIG. 1A is a circuit diagram of a series resonator
- FIG. 1B is a circuit diagram of a parallel resonator
- FIG. 1C is a diagram of a pass characteristic of the series resonator and that of the parallel resonator;
- FIG. 2A is a circuit diagram of a single-stage ladder filter
- FIG. 2B is a diagram of a pass characteristic of the single-stage ladder filter
- FIG. 3A is a circuit diagram of a ladder filter having attenuation poles at the high-frequency side of the ladder filter
- FIG. 3B is a diagram of an attenuation characteristic of the ladder filter
- FIG. 4 is a circuit diagram of a ladder filter in accordance with a comparative example
- FIG. 5A is a diagram of an attenuation characteristic of the ladder filter in accordance with the comparative example, and FIG. 5B is an enlarged view of a pass band illustrated in FIG. 5A ;
- FIG. 6 is a circuit diagram of a duplexer using a ladder filter having an inductor in a series arm
- FIG. 7 is a diagram of a reactance characteristic of a series resonator Sx
- FIG. 8A is a diagram of an attenuation characteristic of a transmission filter F 13 ; and FIG. 8B is an enlarged view of a pass band illustrated in FIG. 8A ;
- FIG. 9 is a plan view of a surface acoustic wave resonator
- FIG. 10A is a diagram of a pass characteristic of a surface acoustic wave resonator
- FIG. 10B is a diagram of a Q value of the surface acoustic wave resonator
- FIG. 11A is a block diagram of an exemplary duplexer
- FIG. 11B is a block diagram of an exemplary RF (Radio Frequency) module in accordance with a first embodiment
- FIG. 12 is a circuit diagram of a duplexer in accordance with the first embodiment
- FIG. 13A is a plan view of a duplexer chip in accordance with the first embodiment
- FIG. 13B is a cross-sectional view taken along a line A 1 -A 1 in FIG. 13A
- FIG. 13C is a plan view of the duplexer
- FIG. 14 is a transparent view of a transmission filter chip installed in the duplexer of the first embodiment.
- FIGS. 15A , 15 B and 15 C are respectively plan views of a package substrate.
- FIG. 1A is a circuit diagram of a series resonator
- FIG. 1B is a circuit diagram of a parallel resonator
- FIG. 1C is a diagram of a pass characteristic of the series resonator and that of the parallel resonator.
- the series resonator has a resonator S 21 having a pair of ports (signal terminals), one of which is an input terminal In and the other is an output terminal Out.
- the parallel resonator has a resonator P 21 having a pair of ports, one of which is connected to a ground terminal and the other is connected to a short-circuit line between the input terminal In and the output terminal Out.
- the horizontal axis of FIG. 1C denotes the frequency, and the vertical axis thereof denotes the amplitude or magnitude.
- the pass characteristic of the series resonator is indicated by a solid line, and that of the parallel resonator is indicated by a broken line.
- the pass characteristic of the series resonator has one resonance point (resonance frequency) f rs and one anti-resonance point (anti-resonance frequency) f as .
- the amplitude is the largest at the resonance point f rs , and is the smallest at the anti-resonance point f as .
- the pass characteristic of the parallel resonator has one resonance point f rp and one anti-resonance point f ap .
- the amplitude is the smallest at the resonance point frp and is the largest at the anti-resonance point f ap .
- FIG. 2A is a circuit diagram of a single-stage ladder filter
- FIG. 2B illustrates a pass characteristic of the ladder filter illustrated in FIG. 2A .
- a series resonator S 22 is connected in series to the input terminal In and the output terminal Out, and a parallel resonator P 22 is connected between the output terminal Out and ground.
- the resonance point f rs of the series resonator S 22 and the anti-resonance point f ap of the parallel resonator P 22 are designed to be approximately equal to each other.
- the horizontal axis of FIG. 2B is the frequency, and the vertical axis thereof is the amplitude.
- the ladder filter in FIG. 2A has a pass characteristic as illustrated in FIG. 2B , which is a combination of the pass characteristic of the series resonator and that of the parallel resonator.
- the amplitude is the largest around the resonance point f rs of the series resonator S 22 and the anti-resonance point f ap of the parallel resonator P 22 , and is the smallest around the anti-resonance point f as of the series resonator S 22 and the resonance point f rp of the parallel resonator P 22 .
- the ladder filter functions as a bandpass filter.
- the frequency f up at the high-frequency end of the pass band is the frequency f as of the anti-resonance point (anti-resonance frequency) of the series resonator S 22 .
- the frequency f down of the low-frequency end of the pass band is the frequency of the resonance point (resonance frequency) f rp of the parallel resonator P 22 .
- FIG. 3A is a circuit diagram of a multi-stage ladder filter
- FIG. 3B is a diagram of an attenuation characteristic of the multi-stage ladder filter.
- the horizontal axis of FIG. 3B is the frequency, and the vertical axis thereof is the amplitude.
- a ladder filter F 11 is composed of series resonators S 1 , S 2 and S 3 , parallel resonators P 1 and P 2 , and inductors L 1 and L 2 .
- the series resonators S 1 , S 2 and S 3 are connected in series to each other between the input terminal In and the output terminal Out.
- the series resonator S 1 is connected to the input terminal In, and the series resonator S 3 is connected to the output terminal Out.
- One end of the parallel resonator P 1 is connected to a node between the series resonators S 1 and S 2 .
- One end of the parallel resonator P 2 is connected to a node between the series resonators S 2 and S 3 .
- the other end of the parallel resonator P 1 and one end of the inductor L 1 are connected in series to each other, and the other end of the inductor L 1 is grounded.
- the other end of the parallel resonator P 2 and one end of the inductor L 2 are connected in series to each other, and the other end of the inductor L 2 is grounded.
- the resonators function as capacitors outside of the pass band.
- the parallel resonator P 1 and the inductor L 1 function as an LC resonance circuit
- the parallel resonator P 2 and the inductor L 2 function as an LC resonance circuit
- the capacitance of each of the parallel resonators P 1 and P 2 is denoted as C p
- the inductance of the inductor L 1 is denoted as L 1
- the resonance frequency f 1 of the LC resonance circuit formed by the parallel resonator P 1 and the inductor L 1 is expressed as follows:
- the resonance frequency f 2 of the LC resonance circuit formed by the parallel resonator P 2 and the inductor L 2 is described in a similar way to the above expression.
- Attenuation poles are formed at the frequencies f 1 and f 2 .
- the frequencies at which the attenuation poles appear can be adjusted.
- the frequencies f 1 and f 2 may be selected so as to be respectively included in a frequency band corresponding to the second harmonic of the pass band of the filter and a frequency band corresponding to the third harmonic thereof. It is thus possible to form the attenuation poles in the second and third harmonics.
- the ladder filter F 11 has two parallel arms, more attenuation poles may be formed by employing more parallel arms and associated inductors. However, an increased number of parallel arms may increase the signal loss in the pass band, and may prevent downsizing of the filter.
- the inductors L 1 and L 2 may be varied to have larger inductance values. For example, in a case where an attenuation pole is formed at the low-frequency side of the pass band (left-hand side in FIG. 3B ), inductance values as large as 1 ⁇ 5 nH may be used. The use of inductors having large inductance values may prevent downsizing of the ladder filter.
- the inductor L 1 or L 2 may function as a choke coil, and sufficient suppression may not be obtained at frequencies higher than those of the pass band. As described above, it is difficult to realize high suppression over the broad band.
- a duplexer 100 R in accordance with the comparative example corresponds to, for example, the W-CDMA (Wideband Code Division Multiple Access) Band 2 system.
- the pass band of a transmission filter F 11 overlaps the transmission band of the W-CDMA Band 2 system that ranges from 1850 MHz to 1910 MHz.
- the pass band of a reception filter F 12 overlaps the reception band of the W-CDMA Band 2 system that ranges from 1930 MHz to 1990 MHz.
- a system in which the transmission band and the reception band are close to each other such as the W-CDMA Band 2 system, may be designed to generate an attenuation pole around the high-frequency end of the pass band of the transmission filter to improve the sharpness, whereby high suppression is ensured in the pass band of the reception filter. It is thus possible to suppress the interference between the filters.
- an inductor may be connected to the parallel arm, as illustrated in FIG. 3A .
- FIG. 4 is a circuit diagram of a duplexer with the ladder filter of the comparative example.
- FIG. 5A illustrates an attenuation characteristic of the ladder filter of the comparative example
- FIG. 5B illustrates an enlarged view of a pass band illustrated in FIG. 5A .
- the duplexer 100 R of the comparative example includes the transmission filter F 11 , the reception filter F 12 , an antenna terminal Ant, a transmission terminal Tx, reception terminals Rx 1 and Rx 2 , and inductors La and Lr.
- the inductor La, the transmission filter F 11 and the reception filter F 12 are connected in parallel with the antenna terminal Ant.
- reception filter F 12 One end of the reception filter F 12 is connected to the antenna terminal Ant and one end of the transmission filter F 11 , and the other end thereof is connected to the two reception terminals Rx 1 and Rx 2 .
- the inductor Lr is connected between the reception terminals Rx 1 and Rx 2 .
- the inductors La and Lr function as those for impedance matching.
- the reception filter F 12 may be a ladder filter.
- the transmission filter F 11 is the ladder filter of the comparative example.
- the transmission filter F 11 is composed of series resonators S 11 ⁇ S 13 , S 2 , S 3 , S 41 ⁇ S 42 , S 5 and S 6 , and parallel resonators P 1 ⁇ P 3 , and inductors L 1 , L 2 and Lg.
- the series resonators S 11 ⁇ S 6 are connected in series to each other.
- One end of the series resonator S 11 is connected to the antenna terminal Ant and one end of the reception filter F 12 .
- One end of the series resonator S 6 is connected in series to the transmission terminal Tx.
- One end of the parallel resonator P 1 is connected in parallel with a node between the series resonator S 13 and the series resonator S 2 , and the other end thereof is connected in series to one end of the inductor L 1 .
- One end of the parallel resonator P 2 is connected in parallel with a node between the series resonator S 3 and the series resonator S 41 .
- One end of the parallel resonator P 3 is connected in parallel with a node between the series resonator S 42 and the series resonator S 5 .
- the other end of the parallel resonator P 2 and the other end of the parallel resonator P 3 are connected in parallel with one end of the inductor L 2 .
- the other end of the inductor L 1 and the other end of the inductor L 2 are connected in parallel with one end of the inductor Lg.
- the other end of the inductor Lg is grounded.
- Table 1 indicates the capacitance values and resonance frequencies of the resonators of the ladder filter of the first comparative example.
- the capacitance of the series resonator S 3 is 1.67 pF, and the resonance frequency thereof is 1901 MHz.
- the capacitance values of the series resonators S 41 and S 42 are 1.491 pF, and the resonance frequencies thereof are 1889 MHz.
- the capacitance value of the series resonator S 5 is 6.49 pF, and the resonance frequency thereof is 1876 MHz.
- the capacitance value of the series resonator S 6 is 9.23 pF, and the resonance frequency thereof is 1881 MHz.
- the capacitance value of the parallel resonator P 1 is 2.317 pF, and the resonance frequency thereof is 1816 MHz.
- the capacitance value of the parallel resonator P 2 is 1.979 pF, and the resonance frequency thereof is 1819 MHz.
- the capacitance value of the parallel resonator P 3 is 2.243 pF, and the resonance frequency thereof is 1820 MHz.
- the inductance values of the inductors L 1 , L 2 and Lg are 0.5 ⁇ 2 nH, for example.
- the resonator functions as a capacitor.
- the attenuation characteristic may be varied over a broader band.
- the amount of attenuation may be increased in a broader band by increasing the ratio C p /C s where C s is the combined capacitance of the series resonator and C p is the combined capacitance of the parallel resonator.
- Such a resonator having increased suppression is referred to as a second comparative example.
- Table 2 illustrates exemplary capacitance values and resonance frequencies of the resonators of a ladder filter in accordance with the second comparative example.
- the circuit configuration of the ladder filter of the second comparative example is the same as illustrated in FIG. 4 , and a description thereof is omitted here.
- the capacitance values of the series resonators S 1 ⁇ S 3 are 3.618 pF, and the capacitance value of the series resonator S 2 is 7.43 pF.
- the capacitance of the series resonator S 3 is 1.558 pF, and the capacitance values of the series resonators S 41 and S 42 are 1.393 pF.
- the capacitance value of the series resonator S 5 is 6.05 pF, and the capacitance value of the series resonator S 6 is 8.93 pF.
- the capacitance value of the parallel resonator P 1 is 2.485 pF.
- the capacitance value of the parallel resonator P 2 is 2.122 pF.
- the capacitance value of the parallel resonator P 3 is 2.405 pF.
- the resonance frequencies of the resonators are the same as those illustrated in Table 1.
- the ratio C p /C s of the combined capacitance of the parallel resonators P 1 ⁇ P 3 to that of the series resonators S 1 ⁇ S 6 of the second comparative example is approximately 10% greater than that of the first comparative example.
- FIG. 5A is a diagram of attenuation characteristics of the ladder filters in accordance with the first and second comparative examples
- FIG. 5B is an enlarged view of pass bands of the first and second comparative examples.
- the horizontal lines are the frequency
- the vertical lines are the amount of attenuation.
- Solid lines are the attenuation characteristics of the ladder filter in accordance with the first embodiment
- dotted lines are the attenuation characteristics of the ladder filter in accordance with the second embodiment.
- frequency ranges A ⁇ E are defined by broken lines.
- the frequency range A is a band used for a portable telephone system.
- the frequency range B is a band used for GPS (Global Positioning System).
- the frequency range C is a band used for a wireless LAN (Local Area Network) and Bluetooth (BT).
- the frequency range D is a band of second harmonics of the transmission filter F 11 .
- the frequency range E is a band of third harmonics of the transmission filter F 11 .
- a range defined by broken lines in FIG. 5B is a transmission band of the W-CDMA band 2 system.
- the first and second comparative examples have attenuation poles generated around the high-frequency ends of the pass bands. This is because the inductors L 1 , L 2 and Lg having high inductance values are connected to the parallel arms.
- the degree of suppress deteriorates at frequencies lower than and higher than those of the pass band.
- the first comparative example has a difficulty in realizing a high degree of suppression over broad bands.
- the second comparative example has a higher degree of suppression than that of the first comparative example without increasing the number of attenuation poles. This is because the capacitance ratio C p /C s is increased, as illustrated in Table 2.
- the second comparative example has a deterioration of about 0.15 ⁇ 0.2 dB even in the pass band.
- the second comparative example has a difficulty in realizing both high suppression over broad bands and low insertion loss.
- the first and second comparative examples the suppression is easily degraded at high frequencies. This is because the inductors L 1 , L 2 and Lg used to form the attenuation poles function as choke coils. The behaviors of the inductors L 1 , L 2 and Lg as choke coils are conspicuous when these inductors have large inductance values.
- an attenuation pole may be formed in the pass band of the other filter.
- the inductors having large inductance values are used to form the attenuation pole, there is a high possibility that realization of high suppression over broad bands may have a difficulty.
- FIG. 6 is a circuit diagram of a duplexer using a ladder filter with an inductor being connected to a series arm. A description of parts similar to those in FIG. 4 is omitted here.
- a transmission filter F 13 of a duplexer 100 L is configured to replace the aforementioned series resonator S 6 with a series resonator Sx connected in series and to have an inductor Ls connected in series to the series resonator Sx.
- One end of the series resonator Sx is connected in series to the series resonator S 5 , and the other end thereof is connected in series to one end of the inductor Ls.
- the other end of the inductor Ls is connected in series to the transmission terminal Tx.
- the series resonator Sx is an additional resonator connected in series between the series resonators S 11 ⁇ S 5 and the transmission terminal Tx.
- the inductor Ls is connected in series to the series resonator Sx and the transmission terminal Tx.
- the transmission terminal Tx corresponds to an input terminal of the transmission filter F 13
- the antenna terminal Ant corresponds to an output terminal of the transmission filter F 13 .
- FIG. 7 is a diagram of a reactance characteristic of the series resonator Sx.
- the horizontal axis is the frequency, and the vertical axis is the reactance.
- the reactance is zero at the resonance frequency f rx .
- the reactance diverges.
- the series resonator Sx functions as a capacitor.
- the series resonator Sx functions as an inductor.
- Table 3 indicates the capacitance values and resonance frequencies of the resonators included in the transmission filter F 13 .
- the capacitance values and resonance frequencies of the parallel resonators P 1 ⁇ P 3 are the same as those of the second comparative example indicated in Table 2.
- the capacitance value of the series resonator Sx is 3.2 pF, and the resonance frequency thereof is 2400 MHz.
- the inductance value of the inductor Ls is 2.2 nH, and the Q value thereof is 40.
- the series resonator S 2 has the highest anti-resonance frequency among the series resonators S 11 ⁇ S 5 except the series resonator Sx.
- the resonance frequency f rx of the series resonator Sx is 2400 MHz, which is higher than the anti-resonance frequency of the series resonator S 2 .
- the resonance frequency f rx of the series resonator Sx is higher than the anti-resonance frequencies of the series resonators S 11 ⁇ S 5 .
- the frequency of the high-frequency end of the pass band of the ladder filter is defined by the anti-resonance frequency of the series resonator.
- the resonance frequency fr x is located at the high-frequency side of the pass band of the transmission filter F 13 .
- the pass band of the transmission filter F 13 corresponds to the range G 1 illustrated in FIG. 7 . Therefore, the series resonator Sx functions as a capacitance in the pass band of the transmission filter F 13 .
- the series resonator Sx and the inductor Ls function as an LC resonance circuit in the passband.
- the resonance frequency f lc of the LC resonance circuit LC 1 is higher than the frequency f down of the low-frequency end of the pass band and is lower than the frequency f up of the high-frequency end thereof. That is, the following relationship stands:
- FIG. 8A is a diagram of an exemplary attenuation characteristic of the transmission filter F 13
- FIG. 8B is an enlarged view of the pass band in FIG. 8A .
- Solid lines are the attenuation characteristic of the transmission filter F 13
- broken lines are the attenuation characteristic of the ladder filter of the first comparative example.
- Dotted lines are the attenuation characteristics of the ladder filter of the second comparative example.
- the transmission filter F 13 has high suppression over a broad band including the frequency ranges A through E.
- the transmission filter F 13 has good characteristics that are as good as or better than those of the transmission filter F 11 of the first comparative example in the pass band, particularly, at the edges of the reception bands of the W-CDMA Band 2 system (around 1850 MHz and around 1910 MHz).
- the resonance frequency f rx of the series resonator Sx is higher than the resonance frequencies of the series resonators S 11 ⁇ S 5 .
- the resonance frequency f rx is located at the high-frequency side of the pass band of the transmission filter F 13 .
- the series resonator Sx functions as a capacitor in the pass band of the transmission filter F 13 .
- the series resonator Sx and the inductor Ls function as the LC resonance circuit LC 1 in the pass band.
- the insertion loss in the pass band can be canceled by the resonance of the LC resonance circuit.
- the resonance frequency f lc may be set around the center frequency of the pass band, for example.
- the LC resonance circuit LC 1 functions as a capacitor, and the capacitance ratio Cp/Cs of the transmission filter F 13 has a larger value.
- the LC resonance circuit LC 1 functions as an inductor, and plays a role of choke coil.
- Attenuation poles are generated around the high-frequency end of the pass band.
- the transmission filter F 13 is capable of generating the attenuation poles and realizing high suppression over the broad band while suppressing increase in the insertion loss in the pass band.
- the series resonator Sx in order to have the series resonator Sx and the inductor Ls function as an LC resonance circuit in the pass band of the transmission filter F 13 , the series resonator Sx is required to function as a capacitor in the pass band. Therefore, the resonance frequency f rx of the series resonator Sx is higher than or lower than the pass band.
- the series resonator Sx functions as an inductor in the frequency range G 3 between the resonance frequency f rx and the anti-resonance frequency f ax .
- the anti-resonance frequency f ax of the series resonator Sx is lower than the resonance frequency of the parallel resonator of the transmission filter F 13 .
- the anti-resonance frequency f ax is preferably lower than the frequency at the low-frequency end of the pass band.
- the pass band corresponds to the frequency range G 2 in FIG. 7
- the series resonator Sx functions as a capacitor.
- FIG. 9 is a plan view of an exemplary SAW resonator.
- the view of FIG. 9 is schematic, and the SAW resonator is not limited to the number of electrode fingers illustrated in FIG. 9 .
- a SAW resonator 10 includes a piezoelectric substrate 12 , an IDT (InterDigital Transducer) 14 and two reflectors 16 .
- the IDT 14 and the reflectors 16 are provided on the piezoelectric substrate 12 .
- the IDT 14 includes a pair of comb-like electrodes 14 a and 14 b that are interleaved with each other, and excites acoustic waves.
- the two reflectors 16 are arranged at both sides of the IDT 14 in directions in which the acoustic waves are propagated.
- the wavelength ⁇ of the acoustic waves depends on the pitch between the electrode fingers of the IDT 14 , and may be 1.62 ⁇ m, for example.
- the aperture length W of the interleaved electrode fingers of the IDT 14 may be 19.9 ⁇ , for example.
- the number of pairs of electrode fingers of the IDT 14 may be 59.5, for example.
- the capacitance of the SAW resonator may be adjusted by varying the pitch between the electrode fingers or the aperture length W of the interleaved electrode fingers.
- the piezoelectric substrate 12 may be made of a piezoelectric substance such as lithium tantalate (LiTaO 3 ) or lithium niobate (LiNbO 3 ), for example.
- the IDT 14 and the reflectors 16 may be made of a metal such as aluminum (Al).
- the Q value of the SAW resonator is defined as a Q value obtained when the SAW resonator 10 functions as a capacitor.
- FIG. 10A is a diagram of an exemplary pass characteristic of the SAW resonator
- FIG. 10B is a diagram of an exemplary Q value thereof.
- the horizontal axis is the frequency
- the vertical axis of FIG. 10A is the amplitude
- the vertical axis of FIG. 10B is the Q value.
- the resonance frequency f r of the SAW resonator 10 is 2332 MHz, and the amplitude is the largest at the resonance frequency f r .
- the anti-resonance frequency f a is 2405 MHz, and the amplitude is the smallest at the anti-resonance frequency f a .
- the Q value is zero around the resonance frequency f r .
- the Q value is about 10.
- the Q value increases at the low-frequency side of the resonance frequency fr.
- the Q value is equal to or larger than 40 at frequencies lower than f q , where fq is 2050 MHz.
- the series resonator Sx functions as a capacitor in the pass band of the transmission filter F 13 .
- the inductor Ls illustrated in FIG. 6 a chip inductor may be used.
- the Q value of the chip inductor included in the ladder filter is about 40, for example.
- the Q value of the series resonator Sx is equal to or larger than 40.
- the Q value is equal to or larger than 40 at the low-frequency side of the resonance frequency f q . It is therefore preferable that the frequency f up of the high-frequency end of the pass band of the transmission filter F 13 is lower than f q , that is, lower than 2050 MHz. In other words, it is preferable that the resonance frequency f rx of the series resonator Sx meets the following condition with respect to the high-frequency end of the pass band of the transmission filter F 13 :
- the frequency f up may be equal to or lower than f q .
- the series resonator Sx functions as a capacitor in the pass band, and forms the LC resonance circuit LC 1 together with the inductor Ls. It is thus possible to obtain high suppression over the broad bands. Since the resonance frequency f lc of the LC resonance circuit LC 1 is located within the pass band, the loss in the pass band can be reduced.
- the resonance frequency f rx of the series resonator Sx may be either higher than the anti-resonance frequency of the series resonator or lower than the resonance frequency of the parallel resonator.
- the resonance frequency f rx is higher than the anti-resonance frequency of the series resonator and satisfies the condition f rx >1.138 ⁇ f up .
- FIG. 11A is a block diagram of an exemplary duplexer in accordance with the first embodiment
- FIG. 11B is a block diagram of an RF module equipped with the duplexer in accordance with the first embodiment.
- a duplexer 100 has a reception filter 100 a and a transmission filter 100 b .
- the reception filter 100 a and the transmission filter 100 b are connected to a common terminal (antenna terminal) 102 .
- the common terminal 102 is connected to an antenna 104 .
- the reception filter 100 a receives a signal from the antenna 104 , and the filtered signal is applied to an amplifier, for example.
- the transmission filter 100 b filters a signal from an amplifier, for example, and the filtered signal is applied to the antenna 104 via which the signal is transmitted.
- an RF module 110 is equipped with an antenna 104 , an antenna switch 112 , a duplexer bank 114 and an amplifier module 116 .
- the RF module 110 corresponds to a plurality of communication systems such as the GSM (Global System for Mobile Communication) system and the W-CDMA system, and is installed in the portable telephone or the like.
- the GSM system handles the 850 MHz band (GSM 850), 900 MHz band (GSM 900), 1800 MHz band (GSM 1800), and 1900 MHz band (GSM 1900).
- the antenna 104 is capable of handling the GSM system and the W-CDMA system.
- the duplexer bank 114 includes a plurality of duplexers 114 a , 114 b and 114 c . Each of the duplexers corresponds to one of the communication systems.
- the duplexer bank 114 may have two duplexers or more than three duplexers.
- the antenna switch 112 selects the duplexer that conforms to the communication system used for signal transmission and reception from among the duplexers of the duplexer bank 114 , and makes a connection between the selected duplexer and the antenna 104 .
- the duplexers 114 a , 114 b and 114 c of the duplexer bank 114 are connected to the amplifier module 116 .
- the amplifier module 116 amplifies the signals received by the reception filters of the duplexers 114 a ⁇ 114 c , and outputs the amplified signal to a next-stage processing part. Further, the amplifier module 116 amplifiers signals generated by a processing part (not illustrated), and outputs the amplified signals to the transmission filters of the duplexers 114 a ⁇ 114 c.
- FIG. 12 is a circuit diagram of the configuration of the duplexer in accordance with the first embodiment.
- the duplexer 100 has a duplexer 101 , which includes structural components other than the inductors La, Lr and Ls.
- the duplexer chip 101 includes a reception filter chip 100 c and a transmission filter chip 100 d .
- the detailed configuration of the duplexer chip 101 will be described later.
- Structural components of the transmission filter other than inductors L 1 , L 2 , Lg and Ls are realized as a transmission filter chip 100 d .
- the inductors La, Lr and Ls are realized by chip inductors.
- the resonance frequencies and capacitance values of the resonators are the same as those described in Table 3.
- the resonance frequency f rx of the series resonator Sx is higher than the anti-resonance frequencies of the series resonators S 11 ⁇ S 5 .
- the resonance frequency f rx satisfies the aforementioned condition f rx >1.138 ⁇ f up .
- the inductance value of the inductor Ls may be 2.2 nH, and the Q value thereof may be 40, for example.
- FIG. 13A is a plan view of the duplexer chip 101
- FIG. 13B is a cross-sectional view taken along a line A 1 -A 1 illustrated in FIG. 13A
- FIG. 13C is a plan view of the duplexer chip 101 .
- the duplexer chip 101 includes the reception filter chip 100 c , the transmission filter chip 100 d , a package substrate 120 and a seal member 122 .
- the view of FIG. 13A is seen through the seal member 122 .
- the reception filter chip 100 c and the transmission filter chip 100 d are flip-chip mounted on the package substrate 120 by bumps 124 .
- the package substrate 120 has a two-layer structure composed of a first layer 120 - 1 and a second layer 120 - 2 located below the first layer 120 - 1 .
- Interconnection layers 120 a , 120 b and 120 c are formed on the upper, intermediate and lower surfaces of the package substrate 120 , which are connected together by via interconnections 26 .
- the interconnection layer 120 b is located between the first layer 120 - 1 and the second layer 120 - 2 .
- the interconnection layer 120 c functions as footpads. Some interconnections provided on or in the package substrate 120 function as inductors.
- the seal member 122 may be made of an insulative material such as epoxy resin or solder, and seals the reception filter chip 100 c and the transmission filter chip 100 d .
- the package substrate 120 may be made of an insulative material such as ceramic.
- the interconnection layers 120 a ⁇ 120 c are made of a metal such as aluminum.
- the bumps 124 may be made of a metal such as gold.
- the duplexer chip 101 is flip-chip mounted on a printed-circuit board 130 via the interconnection layer 120 c .
- the inductors Lr, La and Ls, which are chip inductors, are mounted on the printed-circuit board 130 .
- the antenna terminal Ant, the reception terminals Rx 1 and Rx 2 and the transmission terminal Tx are provided on the printed-circuit board 130 .
- the duplexer chip 101 and the inductor Lr are connected together by interconnection lines 131 r - 1 and 131 r - 2 .
- the interconnection line 131 r - 1 is connected to the reception terminal Rx 1 .
- the interconnection line 131 r - 2 is connected to the reception terminal Rx 2 .
- the duplexer chip 101 and the inductor La are connected together via an interconnection line 131 a .
- the interconnection line 131 a is connected to the antenna terminal Ant.
- the duplexer chip 101 and the inductor Ls are connected together by an interconnection line 131 s .
- the interconnection line 131 s is connected to the transmission terminal Tx.
- the printed-circuit board 130 may be replaced with a module board.
- the RF module 110 illustrated in FIG. 11B is formed by mounting the duplexer chips and the chip inductors on the printed-circuit board 130 or the module board.
- FIG. 14 is a perspective view of the transmission filter chip 100 d of the duplexer configured in accordance with the first embodiment.
- the transmission filter chip 100 d is composed of the piezoelectric substrate 12 , the series resonators S 11 ⁇ Sx, the parallel resonators P 1 ⁇ P 3 , the antenna terminal Ant 1 , the transmission terminal Tx 1 and terminals 18 a and 18 b .
- the series resonators S 11 ⁇ Sx and the parallel resonators P 1 ⁇ P 3 are SAW resonators in which the IDT and the reflectors of each SAW filter are arranged on the piezoelectric substrate 12 .
- the transmission filter chip 100 d is flip-chip mounted so that the surface of the piezoelectric substrate 12 on which the SAW resonators are formed and the upper surface of the package substrate 120 face each other. As illustrated in FIG. 13B , since a spacing is formed between the transmission filter chip 100 d and the package substrate 120 , the acoustic waves are excited without any obstacles.
- One of the comb-like electrodes of the series resonator S 11 is connected to the antenna terminal Ant 1 .
- the antenna terminal Ant 1 is connected to the antenna 104 illustrated in FIG. 11A or 11 B.
- One of the comb-like electrodes of the parallel resonator P 1 is connected to the terminal 18 a .
- the terminal 18 a is connected to the inductor L 1 illustrated in FIG. 12 .
- One of the comb-like electrodes of the parallel resonator P 2 and one of the comb-like electrodes of the parallel resonator P 3 are connected to the terminal 18 b .
- the terminal 18 b is connected to the inductor L 2 illustrated in FIG. 12 .
- the transmission terminal Tx 1 is connected to the transmission terminal Tx via the inductor Ls illustrated in FIGS. 12 and 13C .
- Each terminal is used for flip-chip mounting on the package substrate 120 illustrated in FIG. 13B .
- Circular shapes on the solid patterns are areas in which the bumps 124 are connected.
- FIGS. 15A through 15C are respectively plan views of the package substrate 120 .
- FIG. 15A illustrates the upper surface of the package substrate 120 .
- FIG. 15B illustrates the plan view of the second layer 120 - 2 of the package substrate 120 seen through the first layer 120 - 1 .
- FIG. 15C is a view seen through the first layer 120 - 1 and the second layer 120 - 2 .
- the interconnection layer 120 a is provided on the first layer 120 - 1 .
- the interconnection layer 120 a includes an antenna terminal Ant 2 , a transmission terminal Tx 2 , interconnection lines 20 a , 20 b and 20 c , reception terminals Rx 1 a and Rx 2 a , and a ground terminal GND 1 .
- the transmission filter chip 100 d is mounted in an area surrounded by a broken line in FIG. 15A .
- the antenna terminal Ant 2 of the interconnection layer 120 a is connected to the antenna terminal Ant 1 of the transmission filter chip 100 d .
- the transmission terminal Tx 2 of the interconnection layer 120 a is connected to the transmission terminal Tx 1 of the transmission filter chip 100 d .
- the interconnection line 20 a of the interconnection layer 120 a is connected to the terminal 18 a of the transmission filter chip 100 d .
- the interconnection line 20 b of the interconnection layer 120 a is connected to the terminal 18 b of the transmission filter chip 100 d .
- the interconnection lines 20 a and 20 b are connected to the interconnection line 20 c .
- the interconnection line 20 a contributes to the generation of the inductor L 1 illustrated in FIG. 12 .
- the interconnection line 20 b contributes to the generation of the inductor L 2 .
- the interconnection line 20 c contributes to the generation of the inductor Lg.
- the inductors L 1 , L 2 and Lg are provided on the package substrate 120 .
- the reception terminals Rx 1 a and Rx 2 a are connected to reception terminals included in the footpads of the reception filter chip 100 c .
- the ground terminal GND 1 is connected to a ground terminal included in the footpads of the reception filter chip 100 c.
- the interconnection layer 120 b is provided on the upper surface of the second layer 120 - 2 .
- the interconnection layer 120 b includes an antenna pattern Ant 3 , a transmission pattern Tx 3 , reception patterns Rx 1 b and Rx 2 b , and ground patterns GND 2 b and GND 3 .
- the interconnection layers 120 a and 120 b are connected together by the via interconnections 26 .
- the antenna pattern Ant 3 of the interconnection layer 120 b is connected to the antenna terminal Ant 2 of the interconnection layer 120 a .
- the transmission pattern Tx 3 of the interconnection layer 120 b is connected to the transmission terminal Tx 2 of the interconnection layer 120 a .
- the ground pattern GND 2 b of the interconnection layer 120 b is connected to the interconnection line 20 c of the interconnection layer 120 a .
- the reception pattern Rx 1 b of the interconnection layer 120 b is connected to the reception terminal Rx 1 a of the interconnection layer 120 a .
- the reception pattern Rx 2 b of the interconnection layer 120 b is connected to the reception terminal Rx 2 a of the interconnection layer 120 a .
- the ground pattern GND 3 of the interconnection layer 120 b is connected to the ground terminal GND 1 of the interconnection layer 120 a.
- the interconnection layer 120 c is provided on the lower surface of the second layer 120 - 2 .
- the interconnection layer 120 c includes an antenna terminal Ant 4 , a transmission terminal Tx 4 , reception terminals Rx 1 c and Rx 2 c , and ground terminals GND 2 c , GND 2 d , GND 4 , GND 5 and GND 6 .
- the interconnection layers 120 b and 120 c are connected together by the via interconnections 26 .
- the antenna terminal Ant 4 of the interconnection layer 120 c is connected to the antenna pattern Ant 3 of the interconnection layer 120 b .
- the transmission terminal Tx 4 of the interconnection layer 120 c is connected to the transmission pattern Tx 3 of the interconnection layer 120 b .
- the ground terminals GND 2 c and GND 2 d of the interconnection layer 120 c are connected to the ground pattern GND 2 b of the interconnection layer 120 b .
- the reception terminal Rx 1 c of the interconnection layer 120 c is connected to the reception pattern Rx 1 b of the interconnection layer 120 b .
- the reception terminal Rx 2 c of the interconnection layer 120 c is connected to the reception pattern Rx 2 b of the interconnection layer 120 c .
- the ground terminals GND 4 , GND 5 and GND 6 of the interconnection layer 120 c is connected to the ground pattern GND 3 of the interconnection layer 120 b.
- the transmission filter 100 b of the duplexer 100 in accordance with the first embodiment includes the series resonators S 11 ⁇ S 5 , the parallel resonators P 1 ⁇ P 3 , the series resonator Sx (additional resonator), and the inductor Ls connected in series to the series resonator Sx.
- the resonance frequency f rx of the series resonator Sx is higher than the anti-resonance frequencies of the series resonators S 11 ⁇ S 5 .
- the series resonator Sx functions as a capacitor, and forms the LC resonance circuit LC 1 together with the inductor Ls.
- the transmission filter 100 b realizes high suppression over the broad bands.
- the resonance frequency of the LC resonance circuit LC 1 is located in the pass band of the transmission filter 100 b .
- the insertion loss in the pass band can be reduced.
- the anti-resonance frequency fax of the series resonator Sx may be lower than the resonance frequencies of the parallel resonators P 1 ⁇ P 3 .
- the resonance frequency f rx satisfies the aforementioned condition f rx >1.138 ⁇ f up , the series resonator Sx functions as a capacitor having a Q value of 40 or more.
- the resonance frequency f rx is higher than the anti-resonance frequencies of the series resonators S 11 ⁇ S 5 .
- the aforementioned condition f rx >1.138 ⁇ f up is satisfied.
- the resonator is not the SAW resonator but another type of resonator using IDT such as a Love wave resonator, a Lamb wave resonator, a boundary acoustic wave resonator, a high Q value is obtained by meeting the aforementioned condition f rx >1.138 ⁇ f up .
- the resonator may be a resonator that does not use IDT, such as a piezoelectric thin-film resonator.
- the series resonator Sx that functions as a capacitor is incorporated in the ladder filter.
- the inductors L 1 , L 2 and Lg are formed by the interconnection layers 120 a ⁇ 120 c in the package substrate 120 .
- the duplexer 100 and the RF module 110 may be downsized.
- the inductors La, Ls and Lr may be formed by the interconnection layers 120 a ⁇ 120 c .
- the duplexer 100 and the RF module 110 may further be downsized.
- the attenuation poles are formed around the high-frequency end of the pass band of the transmission filter 100 b , as illustrated in FIG. 8A .
- the transmission filter 100 b has high suppression in the pass band of the reception filter 100 a , whereby interference between the transmission filter 100 b and the reception filter 100 a can be suppressed.
- the first filter is preferably the SAW filter.
- the first filter may be the transmission filter or the reception filter, which may be selected in accordance with the communication system, for example.
- the ladder filter of the first embodiment may be applied to both the filters of the duplexer or may be applied to the second filter. In other words, the duplexer has at least ladder filter of the first embodiment.
- the RF module includes at least one ladder filter of the first embodiment.
- the module of the first embodiment is not limited to the RF module but may be another type of module.
- the module that includes multiple filters on the single module board and utilizes multiple bands is capable of ensuring suppression over the board bands and having improved characteristics.
- the first embodiment is not limited to the aforementioned duplexer and the module with the duplexer but may be a ladder filter alone.
- the ladder filter is not limited to the multiple-stage configuration but may have only a single stage.
- the ladder filter includes one or multiple series resonators and one or multiple parallel resonators.
- the resonance frequency f rx of the series resonator Sx is higher than the anti-resonance frequencies of one or the multiple series resonators.
- the anti-resonance frequency f ax of the series resonator Sx is lower than the resonance frequencies of one or the multiple parallel resonators.
- the series resonator Sx functions as a capacitor in the pass band of the ladder filter.
- the series resonator Sx (additional resonator) and the inductor Ls may be provided between the series resonator and the antenna terminal Ant (output terminal).
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Abstract
Description
- This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2011-100193, filed on Apr. 27, 2011, the entire contents of which are incorporated herein by reference.
- A certain aspect of the present invention relates to ladder filters, duplexers and modules.
- Recently, portable telephones and portable information terminals have rapidly spread due to the development of mobile communication systems. Thus, there is an increasing demand for RF filters, particularly, those having a compact size and a sharp characteristic. The filters are required to generate an attenuation pole and have sufficient suppression over a broad band in order to handle a new communication system. Such filters may be a ladder filter in which multiple resonators are connected. A duplexer or module equipped with filters is required to have transmission and reception filters configured so that the transmission filter has high suppression in the pass band of the reception filter and the reception filter has high suppression in the pass band of the transmission filter. There is a proposal of a filter equipped with an inductor in order to adjust the filter characteristics.
- Japanese Patent Application Publication No. 6-350390 (Document 1) discloses a resonator with which an LC resonance circuit is connected in parallel. Japanese Patent Application Publication No. 11-55067 (Document 2) discloses a ladder filter to which an inductor is connected. The arts disclosed in
Documents - According to an aspect of the present invention, there are provided a ladder filter, a duplexer and a module having high suppression over a broad band.
- According to another aspect of the present invention, there is provided a ladder filter including: at least one series resonator connected in series between an input terminal and an output terminal; at least one parallel resonator connected in parallel with the at least one series resonator; an additional resonator connected in series between the at least one series resonator and one of the input terminal and the output terminal; and an inductor connected to the additional resonator in series, the additional resonator having a resonance frequency higher than an anti-resonance frequency of the at least one series resonator.
-
FIG. 1A is a circuit diagram of a series resonator,FIG. 1B is a circuit diagram of a parallel resonator, andFIG. 1C is a diagram of a pass characteristic of the series resonator and that of the parallel resonator; -
FIG. 2A is a circuit diagram of a single-stage ladder filter, andFIG. 2B is a diagram of a pass characteristic of the single-stage ladder filter; -
FIG. 3A is a circuit diagram of a ladder filter having attenuation poles at the high-frequency side of the ladder filter, andFIG. 3B is a diagram of an attenuation characteristic of the ladder filter; -
FIG. 4 is a circuit diagram of a ladder filter in accordance with a comparative example; -
FIG. 5A is a diagram of an attenuation characteristic of the ladder filter in accordance with the comparative example, andFIG. 5B is an enlarged view of a pass band illustrated inFIG. 5A ; -
FIG. 6 is a circuit diagram of a duplexer using a ladder filter having an inductor in a series arm; -
FIG. 7 is a diagram of a reactance characteristic of a series resonator Sx; -
FIG. 8A is a diagram of an attenuation characteristic of a transmission filter F13; andFIG. 8B is an enlarged view of a pass band illustrated inFIG. 8A ; -
FIG. 9 is a plan view of a surface acoustic wave resonator; -
FIG. 10A is a diagram of a pass characteristic of a surface acoustic wave resonator; andFIG. 10B is a diagram of a Q value of the surface acoustic wave resonator; -
FIG. 11A is a block diagram of an exemplary duplexer, andFIG. 11B is a block diagram of an exemplary RF (Radio Frequency) module in accordance with a first embodiment; -
FIG. 12 is a circuit diagram of a duplexer in accordance with the first embodiment; -
FIG. 13A is a plan view of a duplexer chip in accordance with the first embodiment,FIG. 13B is a cross-sectional view taken along a line A1-A1 inFIG. 13A , andFIG. 13C is a plan view of the duplexer; -
FIG. 14 is a transparent view of a transmission filter chip installed in the duplexer of the first embodiment; and -
FIGS. 15A , 15B and 15C are respectively plan views of a package substrate. - A ladder filter is now described.
FIG. 1A is a circuit diagram of a series resonator,FIG. 1B is a circuit diagram of a parallel resonator, andFIG. 1C is a diagram of a pass characteristic of the series resonator and that of the parallel resonator. - As illustrated in
FIG. 1A , the series resonator has a resonator S21 having a pair of ports (signal terminals), one of which is an input terminal In and the other is an output terminal Out. As illustrated inFIG. 1B , the parallel resonator has a resonator P21 having a pair of ports, one of which is connected to a ground terminal and the other is connected to a short-circuit line between the input terminal In and the output terminal Out. - The horizontal axis of
FIG. 1C denotes the frequency, and the vertical axis thereof denotes the amplitude or magnitude. The pass characteristic of the series resonator is indicated by a solid line, and that of the parallel resonator is indicated by a broken line. As illustrated inFIG. 1C , the pass characteristic of the series resonator has one resonance point (resonance frequency) frs and one anti-resonance point (anti-resonance frequency) fas. The amplitude is the largest at the resonance point frs, and is the smallest at the anti-resonance point fas. The pass characteristic of the parallel resonator has one resonance point frp and one anti-resonance point fap. The amplitude is the smallest at the resonance point frp and is the largest at the anti-resonance point fap. -
FIG. 2A is a circuit diagram of a single-stage ladder filter, andFIG. 2B illustrates a pass characteristic of the ladder filter illustrated inFIG. 2A . - As illustrated in
FIG. 2A , a series resonator S22 is connected in series to the input terminal In and the output terminal Out, and a parallel resonator P22 is connected between the output terminal Out and ground. The resonance point frs of the series resonator S22 and the anti-resonance point fap of the parallel resonator P22 are designed to be approximately equal to each other. - The horizontal axis of
FIG. 2B is the frequency, and the vertical axis thereof is the amplitude. The ladder filter inFIG. 2A has a pass characteristic as illustrated inFIG. 2B , which is a combination of the pass characteristic of the series resonator and that of the parallel resonator. The amplitude is the largest around the resonance point frs of the series resonator S22 and the anti-resonance point fap of the parallel resonator P22, and is the smallest around the anti-resonance point fas of the series resonator S22 and the resonance point frp of the parallel resonator P22. The ladder filter inFIG. 2A has a pass band between the resonance frequency frp of the parallel resonator P22 and the anti-resonance point fas of the series resonator S22, and has an attenuation range equal to or lower than the resonance frequency frp of the parallel resonator P22 and that equal to or higher than the anti-resonance point fas of the series resonator S22. Thus, the ladder filter functions as a bandpass filter. The frequency fup at the high-frequency end of the pass band is the frequency fas of the anti-resonance point (anti-resonance frequency) of the series resonator S22. The frequency fdown of the low-frequency end of the pass band is the frequency of the resonance point (resonance frequency) frp of the parallel resonator P22. - A ladder filter having an attenuation pole at a harmonic is now described, and a description of a multi-stage ladder filter is followed.
FIG. 3A is a circuit diagram of a multi-stage ladder filter, andFIG. 3B is a diagram of an attenuation characteristic of the multi-stage ladder filter. The horizontal axis ofFIG. 3B is the frequency, and the vertical axis thereof is the amplitude. - As illustrated in
FIG. 3A , a ladder filter F11 is composed of series resonators S1, S2 and S3, parallel resonators P1 and P2, and inductors L1 and L2. The series resonators S1, S2 and S3 are connected in series to each other between the input terminal In and the output terminal Out. The series resonator S1 is connected to the input terminal In, and the series resonator S3 is connected to the output terminal Out. - One end of the parallel resonator P1 is connected to a node between the series resonators S1 and S2. One end of the parallel resonator P2 is connected to a node between the series resonators S2 and S3. The other end of the parallel resonator P1 and one end of the inductor L1 are connected in series to each other, and the other end of the inductor L1 is grounded. The other end of the parallel resonator P2 and one end of the inductor L2 are connected in series to each other, and the other end of the inductor L2 is grounded. The resonators function as capacitors outside of the pass band. Thus, the parallel resonator P1 and the inductor L1 function as an LC resonance circuit, and the parallel resonator P2 and the inductor L2 function as an LC resonance circuit. It is assumed that the capacitance of each of the parallel resonators P1 and P2 is denoted as Cp, and the inductance of the inductor L1 is denoted as L1. In this case, the resonance frequency f1 of the LC resonance circuit formed by the parallel resonator P1 and the inductor L1 is expressed as follows:
-
- The resonance frequency f2 of the LC resonance circuit formed by the parallel resonator P2 and the inductor L2 is described in a similar way to the above expression.
- As illustrated in
FIG. 3B , attenuation poles are formed at the frequencies f1 and f2. By adjusting the capacitance value of the parallel resonator and the inductance value of the inductor, the frequencies at which the attenuation poles appear can be adjusted. For example, the frequencies f1 and f2 may be selected so as to be respectively included in a frequency band corresponding to the second harmonic of the pass band of the filter and a frequency band corresponding to the third harmonic thereof. It is thus possible to form the attenuation poles in the second and third harmonics. - Although the ladder filter F11 has two parallel arms, more attenuation poles may be formed by employing more parallel arms and associated inductors. However, an increased number of parallel arms may increase the signal loss in the pass band, and may prevent downsizing of the filter. Further, in a case where an attenuation pole is formed in a low-frequency range, the inductors L1 and L2 may be varied to have larger inductance values. For example, in a case where an attenuation pole is formed at the low-frequency side of the pass band (left-hand side in
FIG. 3B ), inductance values as large as 1˜5 nH may be used. The use of inductors having large inductance values may prevent downsizing of the ladder filter. At the high-frequency side of the pass band, the inductor L1 or L2 may function as a choke coil, and sufficient suppression may not be obtained at frequencies higher than those of the pass band. As described above, it is difficult to realize high suppression over the broad band. - A comparative example is now described. A
duplexer 100R in accordance with the comparative example corresponds to, for example, the W-CDMA (Wideband Code Division Multiple Access)Band 2 system. The pass band of a transmission filter F11 overlaps the transmission band of the W-CDMA Band 2 system that ranges from 1850 MHz to 1910 MHz. The pass band of a reception filter F12 overlaps the reception band of the W-CDMA Band 2 system that ranges from 1930 MHz to 1990 MHz. For example, a system in which the transmission band and the reception band are close to each other, such as the W-CDMA Band 2 system, may be designed to generate an attenuation pole around the high-frequency end of the pass band of the transmission filter to improve the sharpness, whereby high suppression is ensured in the pass band of the reception filter. It is thus possible to suppress the interference between the filters. In order to generate the attenuation pole, an inductor may be connected to the parallel arm, as illustrated inFIG. 3A . -
FIG. 4 is a circuit diagram of a duplexer with the ladder filter of the comparative example.FIG. 5A illustrates an attenuation characteristic of the ladder filter of the comparative example, andFIG. 5B illustrates an enlarged view of a pass band illustrated inFIG. 5A . - Referring to
FIG. 4 , theduplexer 100R of the comparative example includes the transmission filter F11, the reception filter F12, an antenna terminal Ant, a transmission terminal Tx, reception terminals Rx1 and Rx2, and inductors La and Lr. The inductor La, the transmission filter F11 and the reception filter F12 are connected in parallel with the antenna terminal Ant. - One end of the reception filter F12 is connected to the antenna terminal Ant and one end of the transmission filter F11, and the other end thereof is connected to the two reception terminals Rx1 and Rx2. The inductor Lr is connected between the reception terminals Rx1 and Rx2. The inductors La and Lr function as those for impedance matching. The reception filter F12 may be a ladder filter.
- The transmission filter F11 is the ladder filter of the comparative example. The transmission filter F11 is composed of series resonators S11˜S13, S2, S3, S41˜S42, S5 and S6, and parallel resonators P1˜P3, and inductors L1, L2 and Lg. The series resonators S11˜S6 are connected in series to each other. One end of the series resonator S11 is connected to the antenna terminal Ant and one end of the reception filter F12. One end of the series resonator S6 is connected in series to the transmission terminal Tx.
- One end of the parallel resonator P1 is connected in parallel with a node between the series resonator S13 and the series resonator S2, and the other end thereof is connected in series to one end of the inductor L1. One end of the parallel resonator P2 is connected in parallel with a node between the series resonator S3 and the series resonator S41. One end of the parallel resonator P3 is connected in parallel with a node between the series resonator S42 and the series resonator S5. The other end of the parallel resonator P2 and the other end of the parallel resonator P3 are connected in parallel with one end of the inductor L2. The other end of the inductor L1 and the other end of the inductor L2 are connected in parallel with one end of the inductor Lg. The other end of the inductor Lg is grounded. Next, a description is given of the capacitances and resonance frequencies of the resonators included in the ladder filter of the comparative example (transmission filter F11).
- Table 1 indicates the capacitance values and resonance frequencies of the resonators of the ladder filter of the first comparative example.
-
TABLE 1 Resonator Capacitance [pF] Resonance frequency [MHz] S11 3.879 1881 S12 3.879 1881 S13 3.879 1881 S2 7.8 1968 S3 1.67 1901 S41 1.491 1889 S42 1.491 1889 S5 6.49 1876 S6 9.23 1881 P1 2.317 1816 P2 1.979 1819 P3 2.243 1820
As indicated in Table 1, the capacitance values of the series resonators S11˜S13 are 3.879 pF, and the resonance frequencies thereof are 1881 MHz. The capacitance value of the series resonator S2 is 7.8 pF, and the resonance frequency thereof is 1968 MHz. The capacitance of the series resonator S3 is 1.67 pF, and the resonance frequency thereof is 1901 MHz. The capacitance values of the series resonators S41 and S42 are 1.491 pF, and the resonance frequencies thereof are 1889 MHz. The capacitance value of the series resonator S5 is 6.49 pF, and the resonance frequency thereof is 1876 MHz. The capacitance value of the series resonator S6 is 9.23 pF, and the resonance frequency thereof is 1881 MHz. The capacitance value of the parallel resonator P1 is 2.317 pF, and the resonance frequency thereof is 1816 MHz. The capacitance value of the parallel resonator P2 is 1.979 pF, and the resonance frequency thereof is 1819 MHz. The capacitance value of the parallel resonator P3 is 2.243 pF, and the resonance frequency thereof is 1820 MHz. The inductance values of the inductors L1, L2 and Lg are 0.5˜2 nH, for example. - As described above, outside of the pass band, the resonator functions as a capacitor. By adjusting the capacitance of the resonator, the attenuation characteristic may be varied over a broader band. For example, the amount of attenuation may be increased in a broader band by increasing the ratio Cp/Cs where Cs is the combined capacitance of the series resonator and Cp is the combined capacitance of the parallel resonator. Such a resonator having increased suppression is referred to as a second comparative example.
- Table 2 illustrates exemplary capacitance values and resonance frequencies of the resonators of a ladder filter in accordance with the second comparative example. The circuit configuration of the ladder filter of the second comparative example is the same as illustrated in
FIG. 4 , and a description thereof is omitted here. -
TABLE 2 Resonator Capacitance [pF] Resonance frequency [MHz] S11 3.618 1881 S12 3.618 1881 S13 3.618 1881 S2 7.43 1968 S3 1.558 1901 S41 1.393 1889 S42 1.393 1889 S5 6.05 1876 S6 8.93 1881 P1 2.485 1816 P2 2.122 1819 P3 2.405 1820 - As indicated in Table 2, the capacitance values of the series resonators S1˜S3 are 3.618 pF, and the capacitance value of the series resonator S2 is 7.43 pF. The capacitance of the series resonator S3 is 1.558 pF, and the capacitance values of the series resonators S41 and S42 are 1.393 pF. The capacitance value of the series resonator S5 is 6.05 pF, and the capacitance value of the series resonator S6 is 8.93 pF. The capacitance value of the parallel resonator P1 is 2.485 pF. The capacitance value of the parallel resonator P2 is 2.122 pF. The capacitance value of the parallel resonator P3 is 2.405 pF. The resonance frequencies of the resonators are the same as those illustrated in Table 1. The ratio Cp/Cs of the combined capacitance of the parallel resonators P1˜P3 to that of the series resonators S1˜S6 of the second comparative example is approximately 10% greater than that of the first comparative example.
- A description is now given of results of calculation of the attenuation characteristics of the first and second comparative examples.
FIG. 5A is a diagram of attenuation characteristics of the ladder filters in accordance with the first and second comparative examples, andFIG. 5B is an enlarged view of pass bands of the first and second comparative examples. InFIGS. 5A and 5B , the horizontal lines are the frequency, and the vertical lines are the amount of attenuation. Solid lines are the attenuation characteristics of the ladder filter in accordance with the first embodiment, and dotted lines are the attenuation characteristics of the ladder filter in accordance with the second embodiment. InFIG. 5A , frequency ranges A˜E are defined by broken lines. The frequency range A is a band used for a portable telephone system. The frequency range B is a band used for GPS (Global Positioning System). The frequency range C is a band used for a wireless LAN (Local Area Network) and Bluetooth (BT). The frequency range D is a band of second harmonics of the transmission filter F11. The frequency range E is a band of third harmonics of the transmission filter F11. A range defined by broken lines inFIG. 5B is a transmission band of the W-CDMA band 2 system. - As illustrated in
FIG. 5A , the first and second comparative examples have attenuation poles generated around the high-frequency ends of the pass bands. This is because the inductors L1, L2 and Lg having high inductance values are connected to the parallel arms. In the first comparative example, the degree of suppress deteriorates at frequencies lower than and higher than those of the pass band. Thus, the first comparative example has a difficulty in realizing a high degree of suppression over broad bands. The second comparative example has a higher degree of suppression than that of the first comparative example without increasing the number of attenuation poles. This is because the capacitance ratio Cp/Cs is increased, as illustrated in Table 2. - However, as illustrated in
FIG. 5B , the second comparative example has a deterioration of about 0.15˜0.2 dB even in the pass band. Thus, the second comparative example has a difficulty in realizing both high suppression over broad bands and low insertion loss. Further, the first and second comparative examples, the suppression is easily degraded at high frequencies. This is because the inductors L1, L2 and Lg used to form the attenuation poles function as choke coils. The behaviors of the inductors L1, L2 and Lg as choke coils are conspicuous when these inductors have large inductance values. As has been described, in the duplexers or modules that conform to a system in which the reception band and the transmission band are close to each other like the W-CDMA band 2 system, an attenuation pole may be formed in the pass band of the other filter. When the inductors having large inductance values are used to form the attenuation pole, there is a high possibility that realization of high suppression over broad bands may have a difficulty. - A description is now given of a ladder filter in which an inductor is connected to a series arm.
FIG. 6 is a circuit diagram of a duplexer using a ladder filter with an inductor being connected to a series arm. A description of parts similar to those inFIG. 4 is omitted here. - As illustrated in
FIG. 6 , a transmission filter F13 of aduplexer 100L is configured to replace the aforementioned series resonator S6 with a series resonator Sx connected in series and to have an inductor Ls connected in series to the series resonator Sx. One end of the series resonator Sx is connected in series to the series resonator S5, and the other end thereof is connected in series to one end of the inductor Ls. The other end of the inductor Ls is connected in series to the transmission terminal Tx. The series resonator Sx is an additional resonator connected in series between the series resonators S11˜S5 and the transmission terminal Tx. The inductor Ls is connected in series to the series resonator Sx and the transmission terminal Tx. The transmission terminal Tx corresponds to an input terminal of the transmission filter F13, and the antenna terminal Ant corresponds to an output terminal of the transmission filter F13. Next, the reactance characteristic of the series resonator Sx is described. -
FIG. 7 is a diagram of a reactance characteristic of the series resonator Sx. The horizontal axis is the frequency, and the vertical axis is the reactance. Referring toFIG. 7 , the reactance is zero at the resonance frequency frx. At the anti-resonance frequency fax, the reactance diverges. In a range G1 equal or lower than the resonance frequency frx and a range G2 equal to or higher than the anti-resonance frequency fax, the series resonator Sx functions as a capacitor. In a range G3 between the resonance frequency frx and the anti-resonance frequency fax, the series resonator Sx functions as an inductor. Now, a description is given of the capacitance and the resonance frequency of the resonators and the inductance value of the inductor included in the transmission filter F13. - Table 3 indicates the capacitance values and resonance frequencies of the resonators included in the transmission filter F13.
-
TABLE 3 Resonator Capacitance [pF] Resonance frequency [MHz] S11 3.879 1881 S12 3.879 1881 S13 3.879 1881 S2 7.8 1968 S3 1.67 1901 S41 1.491 1889 S42 1.491 1889 S5 4.964 1870 Sx 3.2 2400 P1 2.485 1816 P2 2.122 1819 P3 2.405 1820
As indicated inFIG. 3 , the capacitance values and resonance frequencies of the series resonators S11˜S42 are the same as those of the comparative example 1 indicated in Table 1. The capacitance value of the series resonator S5 is 4.964 pF, and the resonance frequency thereof is 1870 MHz. The capacitance values and resonance frequencies of the parallel resonators P1˜P3 are the same as those of the second comparative example indicated in Table 2. The capacitance value of the series resonator Sx is 3.2 pF, and the resonance frequency thereof is 2400 MHz. The inductance value of the inductor Ls is 2.2 nH, and the Q value thereof is 40. - In the transmission filter F13, the series resonator S2 has the highest anti-resonance frequency among the series resonators S11˜S5 except the series resonator Sx. As indicated in Table 3, the resonance frequency frx of the series resonator Sx is 2400 MHz, which is higher than the anti-resonance frequency of the series resonator S2. In other words, the resonance frequency frx of the series resonator Sx is higher than the anti-resonance frequencies of the series resonators S11˜S5. As indicated in
FIG. 2B , the frequency of the high-frequency end of the pass band of the ladder filter is defined by the anti-resonance frequency of the series resonator. Thus, the resonance frequency frx is located at the high-frequency side of the pass band of the transmission filter F13. In this case, the pass band of the transmission filter F13 corresponds to the range G1 illustrated inFIG. 7 . Therefore, the series resonator Sx functions as a capacitance in the pass band of the transmission filter F13. As a result, the series resonator Sx and the inductor Ls function as an LC resonance circuit in the passband. - It is assumed that the capacitance of the series resonator Sx is Cx and the inductance of the inductor Ls is Lx. The resonance frequency flc of an LC resonance circuit LC1 formed by the series resonator Sx and the inductor Ls is expressed as follows:
-
- The resonance frequency flc of the LC resonance circuit LC1 is higher than the frequency fdown of the low-frequency end of the pass band and is lower than the frequency fup of the high-frequency end thereof. That is, the following relationship stands:
-
f down<1/(2π(C x ·L x)1/2)<f up - Next, a description is given of results of calculation of the attenuation characteristic of the transmission filter F13.
FIG. 8A is a diagram of an exemplary attenuation characteristic of the transmission filter F13, andFIG. 8B is an enlarged view of the pass band inFIG. 8A . Solid lines are the attenuation characteristic of the transmission filter F13, and broken lines are the attenuation characteristic of the ladder filter of the first comparative example. Dotted lines are the attenuation characteristics of the ladder filter of the second comparative example. - As illustrated in
FIG. 8A , the transmission filter F13 has high suppression over a broad band including the frequency ranges A through E. As illustrated inFIG. 8B , the transmission filter F13 has good characteristics that are as good as or better than those of the transmission filter F11 of the first comparative example in the pass band, particularly, at the edges of the reception bands of the W-CDMA Band 2 system (around 1850 MHz and around 1910 MHz). - A description is given of a mechanism obtained from the attenuation characteristics illustrated in
FIGS. 8A and 8B . As has been described, the resonance frequency frx of the series resonator Sx is higher than the resonance frequencies of the series resonators S11˜S5. In other words, the resonance frequency frx is located at the high-frequency side of the pass band of the transmission filter F13. Thus, the series resonator Sx functions as a capacitor in the pass band of the transmission filter F13. The series resonator Sx and the inductor Ls function as the LC resonance circuit LC1 in the pass band. From the relationship fdown<1/(2π(Cx·Lx)1/2)<fup described above, the insertion loss in the pass band can be canceled by the resonance of the LC resonance circuit. The resonance frequency flc may be set around the center frequency of the pass band, for example. - In the frequency range lower than the pass band, the LC resonance circuit LC1 functions as a capacitor, and the capacitance ratio Cp/Cs of the transmission filter F13 has a larger value. Thus, in the low-frequency range, high suppression is available. In the frequency range higher than the pass band, the LC resonance circuit LC1 functions as an inductor, and plays a role of choke coil. Thus, high suppression is available even in the high-frequency range. Attenuation poles are generated around the high-frequency end of the pass band. As described above, the transmission filter F13 is capable of generating the attenuation poles and realizing high suppression over the broad band while suppressing increase in the insertion loss in the pass band.
- As has been described, in order to have the series resonator Sx and the inductor Ls function as an LC resonance circuit in the pass band of the transmission filter F13, the series resonator Sx is required to function as a capacitor in the pass band. Therefore, the resonance frequency frx of the series resonator Sx is higher than or lower than the pass band. However, as has been described with reference to
FIG. 7 , the series resonator Sx functions as an inductor in the frequency range G3 between the resonance frequency frx and the anti-resonance frequency fax. Thus, even when the resonance frequency frx of the series resonator Sx is lower than the pass band, in a case where the pass band and the frequency range G3 overlap with each other, it may be difficult for the series resonator Sx to function as a capacitor. It is therefore preferable that the anti-resonance frequency fax of the series resonator Sx is lower than the resonance frequency of the parallel resonator of the transmission filter F13. In other words, the anti-resonance frequency fax is preferably lower than the frequency at the low-frequency end of the pass band. In this case, the pass band corresponds to the frequency range G2 inFIG. 7 , and the series resonator Sx functions as a capacitor. - A description is now given of an example in which surface acoustic wave (SAW) resonators are used.
FIG. 9 is a plan view of an exemplary SAW resonator. The view ofFIG. 9 is schematic, and the SAW resonator is not limited to the number of electrode fingers illustrated inFIG. 9 . - Referring to
FIG. 9 , aSAW resonator 10 includes apiezoelectric substrate 12, an IDT (InterDigital Transducer) 14 and tworeflectors 16. TheIDT 14 and thereflectors 16 are provided on thepiezoelectric substrate 12. TheIDT 14 includes a pair of comb-like electrodes reflectors 16 are arranged at both sides of theIDT 14 in directions in which the acoustic waves are propagated. The wavelength λ of the acoustic waves depends on the pitch between the electrode fingers of theIDT 14, and may be 1.62 μm, for example. The aperture length W of the interleaved electrode fingers of theIDT 14 may be 19.9λ, for example. The number of pairs of electrode fingers of theIDT 14 may be 59.5, for example. The capacitance of the SAW resonator may be adjusted by varying the pitch between the electrode fingers or the aperture length W of the interleaved electrode fingers. Thepiezoelectric substrate 12 may be made of a piezoelectric substance such as lithium tantalate (LiTaO3) or lithium niobate (LiNbO3), for example. TheIDT 14 and thereflectors 16 may be made of a metal such as aluminum (Al). - A description is now given of the pass characteristic and Q value of the
SAW resonator 10. The Q value of the SAW resonator is defined as a Q value obtained when theSAW resonator 10 functions as a capacitor. -
FIG. 10A is a diagram of an exemplary pass characteristic of the SAW resonator, andFIG. 10B is a diagram of an exemplary Q value thereof. InFIGS. 10A and 10B , the horizontal axis is the frequency, and the vertical axis ofFIG. 10A is the amplitude, while the vertical axis ofFIG. 10B is the Q value. - As illustrated in
FIG. 10A , the resonance frequency fr of theSAW resonator 10 is 2332 MHz, and the amplitude is the largest at the resonance frequency fr. The anti-resonance frequency fa is 2405 MHz, and the amplitude is the smallest at the anti-resonance frequency fa. As illustrated inFIG. 10B , the Q value is zero around the resonance frequency fr. At the high-frequency side of the resonance frequency fr, the Q value is about 10. At the high-frequency side of the resonance frequency, there are bulk waves that are excited by theIDT 14 and are emitted in thepiezoelectric substrate 12. The bulk waves result in loss and causes a decrease in the Q value. - In contrast, the Q value increases at the low-frequency side of the resonance frequency fr. As illustrated in a left-hand side in
FIG. 10B , the Q value is equal to or larger than 40 at frequencies lower than fq, where fq is 2050 MHz. Thus, the frequency ratio fr/fq=1.138 and fr=1.138×fq - A case is considered where the
SAW resonator 10 is employed as the series resonator Sx. As has been described, in the transmission filter F13 illustrated inFIG. 6 , the series resonator Sx functions as a capacitor in the pass band of the transmission filter F13. As the inductor Ls illustrated inFIG. 6 , a chip inductor may be used. The Q value of the chip inductor included in the ladder filter is about 40, for example. In order to prevent the characteristics of the ladder filter from deteriorating, the Q value of the series resonator Sx is equal to or larger than 40. - As has been described with reference to
FIG. 10B , the Q value is equal to or larger than 40 at the low-frequency side of the resonance frequency fq. It is therefore preferable that the frequency fup of the high-frequency end of the pass band of the transmission filter F13 is lower than fq, that is, lower than 2050 MHz. In other words, it is preferable that the resonance frequency frx of the series resonator Sx meets the following condition with respect to the high-frequency end of the pass band of the transmission filter F13: -
f rx>1.138×f up - Thus, the range on the left-hand side of
FIG. 10B corresponds to the pass band. The frequency fup may be equal to or lower than fq. - As described above, the series resonator Sx functions as a capacitor in the pass band, and forms the LC resonance circuit LC1 together with the inductor Ls. It is thus possible to obtain high suppression over the broad bands. Since the resonance frequency flc of the LC resonance circuit LC1 is located within the pass band, the loss in the pass band can be reduced. The resonance frequency frx of the series resonator Sx may be either higher than the anti-resonance frequency of the series resonator or lower than the resonance frequency of the parallel resonator. However, in the case where the resonator with the IDTs is used for the filter, it is preferable that the resonance frequency frx is higher than the anti-resonance frequency of the series resonator and satisfies the condition frx>1.138×fup.
- Embodiments according to the aspects described above are described below. A first embodiment uses the SAW resonators.
FIG. 11A is a block diagram of an exemplary duplexer in accordance with the first embodiment, andFIG. 11B is a block diagram of an RF module equipped with the duplexer in accordance with the first embodiment. - Referring to
FIG. 11A , aduplexer 100 has a reception filter 100 a and a transmission filter 100 b. The reception filter 100 a and the transmission filter 100 b are connected to a common terminal (antenna terminal) 102. The common terminal 102 is connected to an antenna 104. The reception filter 100 a receives a signal from the antenna 104, and the filtered signal is applied to an amplifier, for example. The transmission filter 100 b filters a signal from an amplifier, for example, and the filtered signal is applied to the antenna 104 via which the signal is transmitted. - Referring to
FIG. 11B , an RF module 110 is equipped with an antenna 104, an antenna switch 112, a duplexer bank 114 and an amplifier module 116. The RF module 110 corresponds to a plurality of communication systems such as the GSM (Global System for Mobile Communication) system and the W-CDMA system, and is installed in the portable telephone or the like. The GSM system handles the 850 MHz band (GSM 850), 900 MHz band (GSM 900), 1800 MHz band (GSM 1800), and 1900 MHz band (GSM 1900). The antenna 104 is capable of handling the GSM system and the W-CDMA system. The duplexer bank 114 includes a plurality of duplexers 114 a, 114 b and 114 c. Each of the duplexers corresponds to one of the communication systems. The duplexer bank 114 may have two duplexers or more than three duplexers. The antenna switch 112 selects the duplexer that conforms to the communication system used for signal transmission and reception from among the duplexers of the duplexer bank 114, and makes a connection between the selected duplexer and the antenna 104. The duplexers 114 a, 114 b and 114 c of the duplexer bank 114 are connected to the amplifier module 116. The amplifier module 116 amplifies the signals received by the reception filters of the duplexers 114 a˜114 c, and outputs the amplified signal to a next-stage processing part. Further, the amplifier module 116 amplifiers signals generated by a processing part (not illustrated), and outputs the amplified signals to the transmission filters of the duplexers 114 a˜114 c. - A description is given of the configuration of the duplexer in accordance with the first embodiment.
FIG. 12 is a circuit diagram of the configuration of the duplexer in accordance with the first embodiment. - Referring to
FIG. 12 , the circuit configuration of theduplexer 100 in accordance with the first embodiment is the same as illustrated inFIG. 6 . Theduplexer 100 has aduplexer 101, which includes structural components other than the inductors La, Lr and Ls. Theduplexer chip 101 includes areception filter chip 100 c and atransmission filter chip 100 d. The detailed configuration of theduplexer chip 101 will be described later. Structural components of the transmission filter other than inductors L1, L2, Lg and Ls are realized as atransmission filter chip 100 d. The inductors La, Lr and Ls are realized by chip inductors. - The resonance frequencies and capacitance values of the resonators are the same as those described in Table 3. The resonance frequency frx of the series resonator Sx is higher than the anti-resonance frequencies of the series resonators S11˜S5. The resonance frequency frx satisfies the aforementioned condition frx>1.138×fup. The inductance value of the inductor Ls may be 2.2 nH, and the Q value thereof may be 40, for example.
-
FIG. 13A is a plan view of theduplexer chip 101, andFIG. 13B is a cross-sectional view taken along a line A1-A1 illustrated inFIG. 13A .FIG. 13C is a plan view of theduplexer chip 101. - As illustrated in
FIGS. 13A and 13B , theduplexer chip 101 includes thereception filter chip 100 c, thetransmission filter chip 100 d, apackage substrate 120 and aseal member 122. The view ofFIG. 13A is seen through theseal member 122. As illustrated inFIG. 13B , thereception filter chip 100 c and thetransmission filter chip 100 d are flip-chip mounted on thepackage substrate 120 bybumps 124. Thepackage substrate 120 has a two-layer structure composed of a first layer 120-1 and a second layer 120-2 located below the first layer 120-1. Interconnection layers 120 a, 120 b and 120 c are formed on the upper, intermediate and lower surfaces of thepackage substrate 120, which are connected together by viainterconnections 26. Theinterconnection layer 120 b is located between the first layer 120-1 and the second layer 120-2. Theinterconnection layer 120 c functions as footpads. Some interconnections provided on or in thepackage substrate 120 function as inductors. Theseal member 122 may be made of an insulative material such as epoxy resin or solder, and seals thereception filter chip 100 c and thetransmission filter chip 100 d. Thepackage substrate 120 may be made of an insulative material such as ceramic. The interconnection layers 120 a˜120 c are made of a metal such as aluminum. Thebumps 124 may be made of a metal such as gold. - As illustrated in
FIG. 13C , theduplexer chip 101 is flip-chip mounted on a printed-circuit board 130 via theinterconnection layer 120 c. The inductors Lr, La and Ls, which are chip inductors, are mounted on the printed-circuit board 130. Although not illustrated, the antenna terminal Ant, the reception terminals Rx1 and Rx2 and the transmission terminal Tx are provided on the printed-circuit board 130. Theduplexer chip 101 and the inductor Lr are connected together byinterconnection lines 131 r-1 and 131 r-2. Theinterconnection line 131 r-1 is connected to the reception terminal Rx1. Theinterconnection line 131 r-2 is connected to the reception terminal Rx2. Theduplexer chip 101 and the inductor La are connected together via aninterconnection line 131 a. Theinterconnection line 131 a is connected to the antenna terminal Ant. Theduplexer chip 101 and the inductor Ls are connected together by aninterconnection line 131 s. Theinterconnection line 131 s is connected to the transmission terminal Tx. - In
FIG. 13C , the printed-circuit board 130 may be replaced with a module board. The RF module 110 illustrated inFIG. 11B is formed by mounting the duplexer chips and the chip inductors on the printed-circuit board 130 or the module board. - The filters of the duplexer are now described.
FIG. 14 is a perspective view of thetransmission filter chip 100 d of the duplexer configured in accordance with the first embodiment. - Referring to
FIG. 14 , thetransmission filter chip 100 d is composed of thepiezoelectric substrate 12, the series resonators S11˜Sx, the parallel resonators P1˜P3, the antenna terminal Ant1, the transmission terminal Tx1 andterminals piezoelectric substrate 12. Thetransmission filter chip 100 d is flip-chip mounted so that the surface of thepiezoelectric substrate 12 on which the SAW resonators are formed and the upper surface of thepackage substrate 120 face each other. As illustrated inFIG. 13B , since a spacing is formed between thetransmission filter chip 100 d and thepackage substrate 120, the acoustic waves are excited without any obstacles. - One of the comb-like electrodes of the series resonator S11 is connected to the antenna terminal Ant1. The antenna terminal Ant1 is connected to the antenna 104 illustrated in
FIG. 11A or 11B. One of the comb-like electrodes of the parallel resonator P1 is connected to the terminal 18 a. The terminal 18 a is connected to the inductor L1 illustrated inFIG. 12 . One of the comb-like electrodes of the parallel resonator P2 and one of the comb-like electrodes of the parallel resonator P3 are connected to the terminal 18 b. The terminal 18 b is connected to the inductor L2 illustrated inFIG. 12 . One of the comb-like electrodes of the series resonator Sx is connected to the transmission terminal Tx1. The transmission terminal Tx1 is connected to the transmission terminal Tx via the inductor Ls illustrated inFIGS. 12 and 13C . Each terminal is used for flip-chip mounting on thepackage substrate 120 illustrated inFIG. 13B . Circular shapes on the solid patterns are areas in which thebumps 124 are connected. - The
package substrate 120 is now described.FIGS. 15A through 15C are respectively plan views of thepackage substrate 120.FIG. 15A illustrates the upper surface of thepackage substrate 120.FIG. 15B illustrates the plan view of the second layer 120-2 of thepackage substrate 120 seen through the first layer 120-1.FIG. 15C is a view seen through the first layer 120-1 and the second layer 120-2. - As illustrated in
FIG. 15A , theinterconnection layer 120 a is provided on the first layer 120-1. Theinterconnection layer 120 a includes an antenna terminal Ant2, a transmission terminal Tx2,interconnection lines transmission filter chip 100 d is mounted in an area surrounded by a broken line inFIG. 15A . The antenna terminal Ant2 of theinterconnection layer 120 a is connected to the antenna terminal Ant1 of thetransmission filter chip 100 d. The transmission terminal Tx2 of theinterconnection layer 120 a is connected to the transmission terminal Tx1 of thetransmission filter chip 100 d. Theinterconnection line 20 a of theinterconnection layer 120 a is connected to the terminal 18 a of thetransmission filter chip 100 d. Theinterconnection line 20 b of theinterconnection layer 120 a is connected to the terminal 18 b of thetransmission filter chip 100 d. The interconnection lines 20 a and 20 b are connected to theinterconnection line 20 c. Theinterconnection line 20 a contributes to the generation of the inductor L1 illustrated inFIG. 12 . Theinterconnection line 20 b contributes to the generation of the inductor L2. Theinterconnection line 20 c contributes to the generation of the inductor Lg. As described above, the inductors L1, L2 and Lg are provided on thepackage substrate 120. The reception terminals Rx1 a and Rx2 a are connected to reception terminals included in the footpads of thereception filter chip 100 c. The ground terminal GND1 is connected to a ground terminal included in the footpads of thereception filter chip 100 c. - Referring to
FIG. 15B , theinterconnection layer 120 b is provided on the upper surface of the second layer 120-2. Theinterconnection layer 120 b includes an antenna pattern Ant3, a transmission pattern Tx3, reception patterns Rx1 b and Rx2 b, and ground patterns GND2 b and GND3. As has been described with reference toFIG. 12B , the interconnection layers 120 a and 120 b are connected together by the viainterconnections 26. Specifically, the antenna pattern Ant3 of theinterconnection layer 120 b is connected to the antenna terminal Ant2 of theinterconnection layer 120 a. The transmission pattern Tx3 of theinterconnection layer 120 b is connected to the transmission terminal Tx2 of theinterconnection layer 120 a. The ground pattern GND2 b of theinterconnection layer 120 b is connected to theinterconnection line 20 c of theinterconnection layer 120 a. The reception pattern Rx1 b of theinterconnection layer 120 b is connected to the reception terminal Rx1 a of theinterconnection layer 120 a. The reception pattern Rx2 b of theinterconnection layer 120 b is connected to the reception terminal Rx2 a of theinterconnection layer 120 a. The ground pattern GND3 of theinterconnection layer 120 b is connected to the ground terminal GND1 of theinterconnection layer 120 a. - Referring to
FIG. 15C , theinterconnection layer 120 c is provided on the lower surface of the second layer 120-2. Theinterconnection layer 120 c includes an antenna terminal Ant4, a transmission terminal Tx4, reception terminals Rx1 c and Rx2 c, and ground terminals GND2 c, GND2 d, GND4, GND5 and GND6. As has been described with reference toFIG. 12B , the interconnection layers 120 b and 120 c are connected together by the viainterconnections 26. Specifically, the antenna terminal Ant4 of theinterconnection layer 120 c is connected to the antenna pattern Ant3 of theinterconnection layer 120 b. The transmission terminal Tx4 of theinterconnection layer 120 c is connected to the transmission pattern Tx3 of theinterconnection layer 120 b. The ground terminals GND2 c and GND2 d of theinterconnection layer 120 c are connected to the ground pattern GND2 b of theinterconnection layer 120 b. The reception terminal Rx1 c of theinterconnection layer 120 c is connected to the reception pattern Rx1 b of theinterconnection layer 120 b. The reception terminal Rx2 c of theinterconnection layer 120 c is connected to the reception pattern Rx2 b of theinterconnection layer 120 c. The ground terminals GND4, GND5 and GND6 of theinterconnection layer 120 c is connected to the ground pattern GND3 of theinterconnection layer 120 b. - The transmission filter 100 b of the
duplexer 100 in accordance with the first embodiment includes the series resonators S11˜S5, the parallel resonators P1˜P3, the series resonator Sx (additional resonator), and the inductor Ls connected in series to the series resonator Sx. The resonance frequency frx of the series resonator Sx is higher than the anti-resonance frequencies of the series resonators S11˜S5. Thus, the series resonator Sx functions as a capacitor, and forms the LC resonance circuit LC1 together with the inductor Ls. As a result, as illustrated inFIGS. 8A and 8B , the transmission filter 100 b realizes high suppression over the broad bands. The resonance frequency of the LC resonance circuit LC1 is located in the pass band of the transmission filter 100 b. Thus, the insertion loss in the pass band can be reduced. - The anti-resonance frequency fax of the series resonator Sx may be lower than the resonance frequencies of the parallel resonators P1˜P3. However, in the case where the resonator is the SAW resonator as illustrated in
FIG. 14 , the resonance frequency frx satisfies the aforementioned condition frx>1.138×fup, the series resonator Sx functions as a capacitor having a Q value of 40 or more. Thus, deterioration of the frequency characteristic is suppressed. As described above, in the case where the SAW resonator is used, it is preferable that the resonance frequency frx is higher than the anti-resonance frequencies of the series resonators S11˜S5. Further, it is preferable that the aforementioned condition frx>1.138×fup is satisfied. In a case where the resonator is not the SAW resonator but another type of resonator using IDT such as a Love wave resonator, a Lamb wave resonator, a boundary acoustic wave resonator, a high Q value is obtained by meeting the aforementioned condition frx>1.138×fup. The resonator may be a resonator that does not use IDT, such as a piezoelectric thin-film resonator. - In the first embodiment, the series resonator Sx that functions as a capacitor is incorporated in the ladder filter. Thus, it is possible to realize compact ladder filters, duplexers and RF modules, as compared with those to which a capacitance element is externally connected. The inductors L1, L2 and Lg are formed by the interconnection layers 120 a˜120 c in the
package substrate 120. Thus, theduplexer 100 and the RF module 110 may be downsized. The inductors La, Ls and Lr may be formed by the interconnection layers 120 a˜120 c. Thus, theduplexer 100 and the RF module 110 may further be downsized. - By using the inductors La and Lr, the attenuation poles are formed around the high-frequency end of the pass band of the transmission filter 100 b, as illustrated in
FIG. 8A . Thus, the transmission filter 100 b has high suppression in the pass band of the reception filter 100 a, whereby interference between the transmission filter 100 b and the reception filter 100 a can be suppressed. Generally, among a first filter of the duplexer and a second filter having a pass band at the high-frequency side of the first filter, namely, having frequencies higher than the frequency at the high-frequency end of the first filter, the first filter is preferably the SAW filter. The first filter may be the transmission filter or the reception filter, which may be selected in accordance with the communication system, for example. The ladder filter of the first embodiment may be applied to both the filters of the duplexer or may be applied to the second filter. In other words, the duplexer has at least ladder filter of the first embodiment. - The RF module includes at least one ladder filter of the first embodiment. The module of the first embodiment is not limited to the RF module but may be another type of module. The module that includes multiple filters on the single module board and utilizes multiple bands is capable of ensuring suppression over the board bands and having improved characteristics.
- As illustrated in
FIGS. 11A and 11B , the first embodiment is not limited to the aforementioned duplexer and the module with the duplexer but may be a ladder filter alone. The ladder filter is not limited to the multiple-stage configuration but may have only a single stage. The ladder filter includes one or multiple series resonators and one or multiple parallel resonators. The resonance frequency frx of the series resonator Sx is higher than the anti-resonance frequencies of one or the multiple series resonators. The anti-resonance frequency fax of the series resonator Sx is lower than the resonance frequencies of one or the multiple parallel resonators. When these conditions are satisfied, the series resonator Sx functions as a capacitor in the pass band of the ladder filter. The series resonator Sx (additional resonator) and the inductor Ls may be provided between the series resonator and the antenna terminal Ant (output terminal). - The present invention is not limited to the specifically disclosed embodiments but may include other embodiments and variations without departing from the scope of the present invention.
Claims (10)
f rx>1.138×f up
f rx>1.138×f up
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JP2011100193A JP5723667B2 (en) | 2011-04-27 | 2011-04-27 | Ladder filter, duplexer and module |
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Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5202652A (en) * | 1989-10-13 | 1993-04-13 | Hitachi, Ltd. | Surface acoustic wave filter device formed on a plurality of piezoelectric substrates |
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-
2011
- 2011-04-27 JP JP2011100193A patent/JP5723667B2/en active Active
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2012
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US9035722B2 (en) | 2015-05-19 |
JP2012231437A (en) | 2012-11-22 |
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